The Triangle Enigmatic
by HalyPooH
Summary: Our favorite triangular kid is literally ripped out of Isabella's hands by our favorite triangular bow tie fitted demon. Ferb, Isabella, and Gretchen, accompanied by Dipper and Mabel, embark on a rather strange journey in order to retrieve him and a long lost Wendy. Will they ever see their friends again? Phinbella, Ferbetchen, DipperXWendy
1. The Calm Before The Storm

**Hi everyone! Sorry about the long wait but I finally got far enough into this story for me to post the first chapter. This _is_ my first crossover, so it's probably not very well put together but hey, at least I tried. :) **

**Gravity Falls fans, the Pines family doesn't come in until later, but I promise they're in here. **

**Pardon Phineas' edginess in this chapter... _he's not quite himself_ _today._**

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It was the usual morning for Isabella: Wake up to the sound of the robins outside the window, bid good morning to Pinky, brush the frizz out of her hair, wash up in the bathroom, and throw on the usual outfit. Today was a Saturday in the month of July, and the weather was in favor for something impossible to happen.

She saw her reflection in the mirror, and gazed at it. It was weird, she thought. What if mirrors themselves were optical illusions and what you always saw yourself looking like was completely off? But then again, cameras and drawings by a certain someone couldn't be wrong. The sixteen year-old took hold of her bottle of black mascara and put a light coat on her eyelashes, examining her iris at the same time. The blue streaks that surrounded her pupil glistened like crystals. No wonder Phineas seemed to always stare into them when they were close. Eyes were interesting things to look at. After closing the bottle, she took up a stick of lip balm and applied it gingerly.

Her mind wondered back to the subject of illusion. Although it might be the most interesting side of it, the looks of something, or what you'd see on the outside, aren't always the most perplexing. Sometimes the inside can be just as tricky and obscure. Isabella wondered that maybe what she always thought herself to be on the inside was just an illusion covering what really was there.

She straightened up in the mirror and messed with the hair in front of her ears a bit. She decided to leave it not tucked behind her ear, as usual, because Phineas took a liking for putting it behind there himself. Maybe she would ask him to braid it for her. She took a long look at her outfit. A pink blouse with a fancy collar covered her upper body, and she wore white shorts that rode high on her waist, making it a possibility to tuck in her shirt without it looking dorky. On her feet she showed off pink flats with lace around the rims. She smiled at her reflection and then dashed out the bedroom door. Her hair flew out behind her as she ran down the hall, descended the stairs, dashed through the kitchen (While grabbing a pre-made cinnamon waffle and giving her mother a wave), and almost attempted to run through the closed front door. She slowed down a tiny bit the open it, and then kicked it closed behind her on the way out.

Isabella couldn't hear any construction going on yet, so she assumed her sixteen and almost seventeen year-old friends were still trying to find something to do today. She made her way across the street and past the garage, and laid her eyes on the all-too-familiar orange swing open gate that would guide her into the backyard. She could already see the two boys with their backs up against the towering oak, which had grown over the height of the house now and provided shade for almost the entire backyard.

She placed a confident hand on the gate and pushed it inward as she walked through. "Hey, Phineas. What'cha dooin?" The ring of her catchphrase resonated through the yard.

The eyes of the boys darted up, but they didn't flinch. Phineas gave her a kind smile while Ferb simply waved once.

"Hi, Isabella! Nothing big yet, but I can feel the gears in my brain turning." The red-head answered her, as always.

"That sounds painful." Ferb furrowed his brow and looked at his stepbrother in disgust.

Isabella sat in the warm grass in front of them and leaned on one hand behind her. The leaves blocked all the direct light except for a few rays, and they fell upon the three teens in random places, casting patterns of leafy shadows on their skin.

"Where are my other two boys?" The girl looked around with an elevated eyebrow.

"Baljeet has another polka recital, and Buford doesn't come unless 'his nerd' is here." Phineas said unpleasantly. "Sometimes I think that they're mentally interrelated, and if you separate them a bomb will go off in some really important major city."

Isabella narrowed her eyes. "And it's weird because they're supposed to be bully and nerd. Enemies, not frenemies."

"We've gone over this _how_ many times now?" Ferb wondered, chuckling amusingly on the side.

"Quite a few, Ferb. Quite a few." Phineas agreed.

"Oh yeah!" Isabella suddenly remembered something. "I just remembered, today's Gretchen's birthday! She said she would be by here around four, so we need to get all of our presents hidden."

"Done and done." Ferb muttered.

"We hid them this morning." Phineas said with a grin. "Along with half the cake."

Isabella eyed him. "Half the cake?"

Phineas chuckled guiltily and looked at Ferb, who cracked a devious smile. "Ferb got hungry after breakfast."

"So you thought the only logical thing was to eat half of the poor birthday girl's cake?" Isabella rolled her eyes.

"Everything else looked so dull compared to it. It was just sitting there all sad in the fridge." The British teen said while he shrugged.

Isabella groaned. "You are a bottomless pit, Ferb! And it doesn't even faze you; you're as ripped as an Olympic swimmer!" She poked his belly, and he flinched.

"He's the man of action, what do you expect?" Phineas joked.

Isabella shook her head in amusement. "I expect nothing but the most incredible." She paused and waited for a moment to get back on the subject of her friend's birthday. "So, how are we gonna do this birthday thing? Do you have a concept down for the yard yet?"

Ferb reached behind him and pulled out a purple binder, flipped through the pages until he found it, and turned it around so she could see.

"We came up with this last night." Phineas explained. "The tree's gonna have streamers coming down off of it like a canopy, and the dance floor will be in there. On the outside of the canopy, we'll have some games set up, including spin the bottle, as she requested. We'll also have helium inflated chairs that'll be attached to the ground to sit in, and an assortment of snacks coming from the Farmer's Market."

Isabella nodded in exultant approval. "Awesome! What about light fixtures? You guys got all that down?"

"Uh-huh. We got spot lights, strobe lights, LED laser pointers, a fancy crystal chandelier to hang on the tree, an assorted array of globular bulb lights to hang among the streamers and across the yard, and some candles for when everything starts to slow down." He gasped. "Oh! And we also have lots of lanterns to hang. They're the kind that you can set into the wind at the end of the night. The squares of the dance floor light up in different colors too."

Isabella seemed pleased. "You guys thought of everything!"

Phineas nudged Ferb. "Oh, that's not even half of it. Ferb took it to himself to make an electronic beat synthesizer. Anyone can create their own music to dance to. The preset sounds are mainly dubstep, and the cool bloopy noises. So we can go and sing on the stage to our own music!"

"You guys are making a stage too?"

"Ferb's rebuilding the same one we used for Love Handel like six years ago."

Isabella looked at Ferb and her eyes grew wide. "You're going all out for this aren't you?"

Ferb shrugged. "She's a nice girl. She deserves a nice party."

"I can't wait until she sees it!"

"You said she was coming around four?" Phineas questioned.

Isabella nodded. "Her mom wanted to take her shopping, so they won't be home until then."

"That's convenient, then. It'll take about an hour or two to get everything set up, and Perry has an appointment at the vet at one." Phineas said, shuffling through a note pad. He looked at a page he had written on earlier that morning, stating everything that was to be done today. He normally didn't need a list to remember it all, but for some reason he just felt like writing at the time. He had also doodled a tiny Isabella on the bottom right corner, so he kept the pad close and made sure his face didn't turn different colors.

"Oh, is something wrong with him?" The girl wondered.

"Yeah, he hasn't been acting like his normal self lately, but it's only inside the house. In the yard, he's the same, but inside he just acts really edgy and it's like he's scared of everything. It's almost like he thinks somebody's watching him in the creepy stalker kind of way."

Isabella frowned slightly. "Well that's strange. Pinky's never done that before… but I guess it's not very accurate to be comparing a dog to a platypus."

Phineas shrugged. "He's pretty much like a dog, except for the obvious stuff that makes him a monotreme."

The girl nodded and narrowed her eyes in acceptance. "Yeah, you're right. He does always behave like a normal dog. Besides like… playing fetch and chasing his tail." She giggled. She brought her hair over her left shoulder and stroked it softly.

"So when are we going to set up the party?" Isabella wondered, looking around at the vacant yard.

"I thought he was going to try and think up something else first, as a side project." Ferb thought, glancing at Isabella and then back to Phineas.

Phineas smiled. "Well, if Isabella wants to get to work on Gretchen's birthday, then we can do that now."

They all stood up from the grass and brushed the pieces off of their clothes. Ferb went inside to retrieve the bulb lights and streamers, while Phineas brought Isabella into the garage to get the chandelier. They had decided to piece together the tree canopy first, since that was going to be the heart of the whole party. It was probably going to be one of the most difficult things to set up, though, because they had to find the perfect branch to hang the chandelier on and they needed to make the streamers and bulbs look like they were coming off of it.

Isabella followed the red-head out of the yard and into the driveway, where he punched in the code for the garage door opener on a side panel. The door opened slowly and loudly, and when there was enough space to slide under, they both ducked their heads and went inside. Isabella's eyes went wide when she saw the beautiful chandelier in the soft light. None of the crystal pieces were put on it yet because it would be too risky to carry all of that glass all the way into the backyard. The crystals were all set in three different wicker baskets on the floor under the table on which the main frame sat.

Phineas stepped up beside her and smiled, and he reached a hand up and stroked the back of her head with it. "Do you think it's big enough?"

Isabella nodded slowly in astonishment. "Phineas, it's the size of my refrigerator!"

The boy giggled. "Just wait until we get all of the jewels on it."

"Have you already put it together?" She wondered, walking forward to look at the assortment of different sized and shaped beautifully carved diamonds. "These are…. These are real diamonds, Phineas!"

Phineas crouched down next to her and picked up one of the beautiful rocks. "We made them ourselves. All we had to do was put some carbon under the pressure of eight hundred fifty thousand per square inch and heat it to the temperature of the Earth's mantle. Of course, normally it would take about four days to make a diamond at that rate, so we multiplied the amount by four and the temperature by two."

"Why not multiply the temperature by four also?"

"We tried that, but the heat started making the machine go all wonky. I guess it couldn't stand that high of a temperature."

Isabella picked up one of the jewels for herself and examined it closely. "How did you carve them this intricately?" She squinted at it.

"Ferb is magical."

Isabella glanced at him and then simply nodded. "I see."

Phineas then stood up and picked up the frame of the soon-to-be chandelier and Isabella took the smallest basket of diamonds. They were quite heavy.

"You got 'em?" Phineas held a hand under the basket when he saw her struggle a bit.

"Yeah." She looked up and smiled. He smiled back, and then they both took the objects into the yard and set them under the tree. They made one more trip to the garage for the other baskets.

Ferb stood under the tree when the two got back from the second trip. He was untangling the bulb lights and straightening them out on the lawn.

To Isabella, something seemed off about today. Something just wasn't right, and she couldn't put a finger on it. Maybe it was because Baljeet and Buford were gone? She wouldn't get this feeling on any other day that they were missing from the group, so that couldn't be it. The inventor and the craftsman were both at ease, and nothing seemed different about them. Phineas was still oblivious yet showing signs of love, and he still spoke in really big manly words. Ferb was still his mysterious yet charming self, the same boy who always made her laugh and who was her best friend since as long as she could remember. But yet, something wasn't blending into the background of it all. Something wasn't fitting. Something didn't belong. But what?

Ferb took out a small hand-held strange looking canon thing and put one end of the lights into it, and then he proceeded in shooting them up to their place in the tree. The lights cascaded from the branches to the roof and back again around ten times, and it formed a shelter of bulbous bulbs. Isabella concluded it would look magnificent when the dark night rolled in.

Phineas used a system of climbing up into the tree to the designated branch so Isabella could hand him the chandelier to hang. He used a thick rope to tie the frame to the tree, pulling it hard to make sure it wouldn't fall.

"Hey Izzy?" He called, and the girl blinked at him in wonder. "Can you make sure this won't fall for me?"

"Sure, Phineas!" Isabella said happily. She then jumped as high as she could and latched onto the metal on the first try. It didn't budge, but it did swing a little. She began to move her legs back and forth, and it swung with her. Phineas giggled at her monkey-like actions.

"Do a flip." Ferb suggested as he watched her.

The girl grinned and beat her legs back and forth until she gathered enough momentum to perform the proposed trick.

"Izzy, don't do it, Ferb's a dumb butt!" Phineas shouted worriedly from the shaking branch above her. He backed up off of it and got in the center of the tree, then made his way down the trunk.

Isabella took one last thrust forward, and she had the confidence in herself that she would make it. Or perhaps it was the confidence that someone would catch her before she would break her sorry behind. She leapt through the thick air and tucked her appendages into her chest, and she did one full spin in the air before coming to a final (but incomplete) stop in the arms of Phineas. He then stumbled backwards and fell into Ferb, who managed to keep him up on his legs.

When the stop became complete, Isabella looked up at her knight in shining armor, and gave him an innocent smile. He furrowed his brow.

"ARE WE ALL FROM CRAZYTOWN!?" Phineas shouted.

Isabella blinked at Phineas and frowned slightly before pointing at the one with green hair. "He's the one who gave me the idea."


	2. A Surprise Visitor

**Long wait, I know. This chapter is a bit cliche but you'll learn later on about something that will make it seem a lot less boring. So please bear with me and just keep reading. Mabel and Dipper will come into play soon! **

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The party was in full swing. Pretty much the whole neighborhood showed up without invitation, but that really didn't bother them since that was a normal thing. Gretchen had been in for a pleasant surprise, and she loved everything about it.

"This is all really nice, Ferb." Gretchen said as she leaned on the snack table. "I mean, compared to all of the other birthdays you and Phineas have done for me, I think this one is exceptionally exquisite."

Ferb nodded in thanks and took a sip of his pineapple punch. It had pineapple sherbet in it, and with a couple extra doses of accidental sugar from Phineas and Isabella. They had decided to actually bake everything instead of call the Farmer's Market. The inventor and the curious girl from across the way had re-baked the half of the cake that was missing. The kitchen was still a mess with flour and egg everywhere, so they had to block off the house and have everyone stay outside.  
"And the cake was simply marvelous. What flavor was it again?" She looked up at the boy and pushed up her glasses so they wouldn't fall off.

"Carrot."

"Oh yeah! I've never had it before." She exclaimed. "Did… did Phineas make it?"

Ferb looked at her in confusion. How could she know that? "Yeah, half of it, why?"

"Ginger found his left shoe in her piece." She put as-a-matter-of-factly.

Ferb frowned slightly and looked at the cake and icing-covered blue converse shoe sitting next to the cake. Now how did Phineas manage to do that?

"Usually Phineas doesn't mess up that bad." She laughed. "Was there something distracting him?"

Ferb smirked. "More like _someone_."

Gretchen looked at him with wide eyes. "Oh my gosh oh my gosh… that's so cute!"

Ferb simply watched her squeal over his brother and his meant-to-be. He missed a lot of what she was saying, something about obliviousness… but she just looked so… different under the lights. The colorful LEDs played on her skin and short sparkly dress in just the right way. Yeah, sure he had considered Gretchen before, but he never really had seen her this way. She was so happy.

But then her hand on his shoulder pulled him back into reality. "FERB!" She said in excitement. "We should play spin the bottle now! It'd be a perfect way to get them to kiss, even if it's just a game, I'm sure it'll still mean something to them."

Ferb smiled. "Yeah. Sounds good to me."

The girl clasped her hands together in anticipation.

The green-haired Brit pushed himself up to a standing position and went to the soda machine they had installed for tonight. It was plugged into the house and sitting off to the side of the yard with the lights glowing dimly on the green grass. There was an assortment of classic drinks to choose from, ranging from simple carton chocolate milk to the glass bottles of Coca-Cola. He pulled a dollar out of his pocket and inserted it into the machine with no trouble, and pushed the big red button labeled "GRAPE EXPLOSION".

A glass robotic hand extended out of the corner and made its way up to the selected drink, and wrapped its claw-like hand around it. It then proceeded to stick it into a tube that carried it down in an elevator-like manner until it came to the level of a flap door through which Ferb took the drink.

He took it back to the chestnut haired girl, and she thanked him. "This will be a perfect bottle to play with." She popped open the lid and took a swig.

Ferb grinned and looked over her shoulder to where his brother was standing with Isabella. He had been with her all night long, which was incredibly amazing if Ferb did say so himself.

All of the other teenagers on the dance floor and scattered about the backyard were either strangers or close friends, and they all looked like they were having a good time, so why not just get a few of the gang members to play, so there wouldn't be too many people. If Phineas ended up having to kiss like… Jenny or something, things would get awkward.

He spotted some of the Fireside girls and Baljeet and Buford sitting at a table nearby.

"So who do you think is worthy of this occasion?" He asked, grinning at her as she chugged the last bit of the GRAPE EXPLOSION down.

Gretchen blinked and looked behind her at the packed dance floor with all its lights and the tables that surrounded it. "Hmm…" She hummed. "Let's just get the regular gang to play." She chuckled. "I'll go fetch them."

So off she went, absent-mindedly strutting down the center of the dance floor like some kind of geeky super model, and unintentionally taking Ferb's breath away. He quickly spun around and walked in the opposite direction, partially in order to get a table ready for the game, and partially so he didn't look like a perv.

Gretchen went to Phineas and Isabella first, and they gladly accepted the challenge (Well, Isabella did, Phineas just kind of stood there with wide eyes while she pulled him after her), and they followed her over to the table where Buford, Baljeet, and the other girls were sitting.

"No way! That's the girliest game out there! Not to mention it ruins relationships." Buford shouted.

Isabella half-lidded her eyes and frowned. "Buford, none of us are even in a relationship. The most it could do is spark one." She glanced at Phineas.

Buford groaned and rolled his eyes. "Why would I wanna do that?" He exclaimed. "I'd rather dunk my own head in a toilet."

"If you don't want to play, Buford, you don't have to, but you're gonna miss out on all the fun!" Milly said with a smile. She, Adyson, Katie, and Ginger stood up from the table and joined them.

"What is spin the bottle?" Baljeet wondered with a lifted finger, trying to get their attention. Ginger grabbed his hand and pulled him along, causing him to shiver.

"It's really fun, Jeet. I think you'll like it."

With that, they all left to go to the table, leaving Buford by himself with Marty the Rabbit Boy.

Buford stared at him and narrowed his eyes. "I know you're not really a rabbit, dude."

Marty blinked and started playing Mozart with his blender. "Prove it."

Buford then groaned and got up to join the others with their stupid game of bottle twirling.

He met the group just as Ferb sat down the empty glass bottle in the center of the circular table. They were situated right in front of the sliding glass doors, and they all had to stand because of the lack of hover chairs. Baljeet and Milly made room for him in-between them.

"Is this everybody's first time playing?" Gretchen wondered, looking about the group with an eager smile.

"Well, duh, Gretch, if anybody had, then they would already have had their first kiss." Katie said melodramatically. Her blonde hair cascaded down her shoulders and her purple streak in her bangs showed her new personality that had come along with puberty.

Gretchen chuckled nervously. "Of course… well then I'll explain the rules." She smiled at all her friends.

"Each person gets a turn to spin the bottle. We'll go around the group clockwise."

A few nods came from Adyson and Isabella.

"The person is to spin the bottle until it lands on a member of the opposite gender. Whoever it lands on, that person has to kiss on either the cheek or the lips. Then the bottle is passed to the next person. It's simple." Gretchen finished.

"So, who wishes to go first?" Ferb said, eyeing everyone in the group.

Everyone was silent.

Gretchen giggled. "Anyone?"

Buford groaned. "This is stupid."

The girl with glasses smiled. "Well okay Buford, you don't have to be so excited!" She slid the bottle over to him with a sly grin.

Buford stared at the bottle and then gave her an angry glare. "I didn't say I wanted to go, but I will just because I know none of you nerds are brave enough to."

They all watched as he gave the bottle a fast spin, and the look on his face went from courageous to quite the opposite as it slowly passed Isabella and Ginger.

It landed right on Adyson.

She looked up at him with wide eyes. "OH HECK TO THE NO!"

Isabella laughed hard. "You gotta do it, it's the rules."

Phineas and Baljeet looked on with amused grins.

Buford sighed and did a shame walk to the other side of the table where she was, and looked at Adyson, who grimaced. He had a blank expression. "I don't want to do this any more than you do, okay?"

Adyson turned to the table and explained loudly, "This means nothing, guys, it's just a game."

Milly and Ginger giggled behind closed fists.

Then Buford planted a tender and fast kiss on her cheek, and turned around quickly to head back to his spot. Adyson blinked and relaxed her shoulders as he left, and her expression had changed to wonder.

"NEXT." Buford said as he pushed the bottle to the person on his left, who coincidentally was Baljeet.

He swallowed uncomfortably and reached a shaky hand out to the bottle, and then gave it a very weak spin. He bit his lip and watched it land… right… on… Buford.

Buford pushed him down into the grass. "NO WAY, NERD."

Baljeet shrieked. "It was not me choosing! It was the bottle combined with the intensity of the force of my spin!"

The bully gave himself a face-palm and turned back to the table, where everyone was giggling hysterically. Baljeet got up and brushed off his rump. He glared at his bully and gave the bottle another spin, this time more forceful. He closed his eyes tightly, waiting eagerly for the sound of the glass against wood to end, and when it did, he kept them closed. "Who did it land on?" He squeaked, and then he felt warm breath on his ear.

"Me." A soft voice rang, and he opened his eyes to see Ginger smiling at him.

Baljeet gave her an awkward smile and chuckled as she turned him around to face her.

"So what do you think, cheek or lips?"

All of the Fireside girls looked on in disgust.

"I-I do not know." He stuttered. "Why not pick for y-yourself?"

Ginger blushed and reached her hands up around his neck, raised herself up on her tip-toes, and gave him a soft kiss to the lips, and they both closed their eyes.

Some of their friends whistled and laughed.

When it was over, the bottle was passed on to the next person, and so on. They shared lots of laughs as both Katie and Isabella had to give Ferb a kiss on the cheek, and he himself had had a good laugh about it.

But then the bottle was passed from Isabella to Phineas, and it was now his turn. He really didn't mind who it landed on, really. _They're all my friends, it's just a game_, he thought. He didn't see Isabella already blushing beside him. She was a nervous wreck. She had tried _numerous_ times tonight to kiss him, almost coming close once or twice. She knew he wanted to kiss her. And he did. But it was constantly getting ironically interrupted.

They had been closer than ever before lately, Phineas and Isabella. Phineas was no longer oblivious, though he kept that to himself. Isabella had been trying so hard to get him to notice her lately, and sometimes the things that she tried made him laugh. It had gotten to the point now that they both new that they liked each other, and both were engaged in this everlasting flirting game. Phineas was a bit reluctant to move to the next level, but Isabella was constantly throwing it out there through hints and gestures that, he admitted, were _very_ convincing.

Everyone watched in silent wonder as Phineas went for the bottle, not holding back at all. He gave Isabella a quick glance that she didn't recognize. Phineas positioned his fingers in such a way that made a certain green-haired man a little suspicious as to what he was up to. Then he flicked them around, and the bottle spun around counter-clockwise in the smack center of the table, almost looking like a game board spinner, and continued to spin for quite some time.

Isabella sighed in annoyance at how long it was taking for it to stop. "Phineas, what kind of spell did you put on it? It's not stopping."

Phineas leaned on the table, and gave her a mischievous look that made her suspect he was up to something. It was the same kind of look he got when plotting out a haunted house to cure a nasty case of the hiccups.

Then, the bottle almost instantly stopped on Isabella. It was kind of freaky how suddenly it stopped. Gasps emanated from all around the table, the loudest coming from Gretchen, Ginger, and Baljeet. Everyone was smiling, nonetheless.

Ah yes, that intricate flick of the hand was a very complicated one indeed. It was so complicated in fact, that it would enable the person spinning it to choose for himself who the bottle would stop on.

Isabella's cheeks could secretly be rose petals right now they were so red. She blinked and looked up at him. Yes, the short little Phineas Flynn had shot up above her height during the eighth grade.

"Why, Phineas… it looks as though the bottle has landed on me." She said, a small smirk growing on her lips.

Phineas smiled back at her with half-lidded eyes, and he reached one hand up to touch the soft strands of her gorgeous raven hair. "I guess it did." He began, slowly pressing his other hand against her back. Her thin blouse made it easy for him to feel the warmth of her skin.

"But you know what?" The boy whispered to her, and only to her.

"What?" She looked up at him in total amazement, not having any idea where this Phineas had come from.

"I wouldn't have it any other way." He said.

Isabella gaped in awe at how close his face was, and she couldn't help but notice the white light that encased each strand of orange on the tip of his head. The white outdoor spherical bulbs that hung loosely overhead cast him in beautiful light, and it made his eyes twinkle with enchantment.

"Who is he and what has he done to Phineas?" Gretchen murmured under her breath.

But just as they began to lean in, the white light slowly changed to yellow, and with it came a strange wind that whistled in their ears and caused everyone to look up.

All of the teens' faces looked on in silent horror at what looked like a yellow triangle with an eye and top hat.

"What in the…" Ferb muttered.

Phineas and Isabella both looked up to see something more than frightening.

"Yyyello, everybody!" The triangle said joyfully, holding his cane up in the air. Isabella held onto Phineas tightly.

"Glad to meet all of you. Not really. I'm just here for the triangle kid." He pointed at Phineas, and with a blast of energy, the boy disappeared right out of the grasp of Isabella. She shrieked in surprise as the warmth turned cold, and she took in a sharp breath. "PHINEAS!"

Ferb stepped forward with wide eyes and an outstretched arm.

"Oh my goodness…" Baljeet said as he hid behind Buford.

The triangle giggled and examined his nails. "Alright, well, that's all I was sent for. Sorry about your loss!" He laughed. "Goodbye!"

With that, he completely vanished from their eyes, and the teens were left with only fear and the horrible grip of surprise squeezing at their hearts.

"Phineas…" Ferb said quietly.

"COME BACK HERE!" Isabella screamed at the empty air. She leapt up onto the table and screamed more threats at the sky while both Buford and the Fireside girls attempted to get her down. "I WILL FIND YOU! WHOEVER YOU ARE, I WILL FIND YOU AND I WILL GET MY PHINEAS BACK!"

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**Now what did I tell you? ;) Now this, my friends, is where the _actual_ party starts. Please review!  
**


	3. Getting Down to Business

**Still no Dipper and Mabel, sorry. They come in the next chapter, I promise. Since I write mainly for PnF, I'm just so used to their characters and its easier for me to start with them. Anyway, enjoy! :)**

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"Come back… come back…" Isabella murmured between quiet sobs and breaths for air. She had her arms stretched out in the air above her and her eyes were clouded with pain. Ferb gently stepped up on the table and tried to comfort her by wrapped arms around her, but she continued to cry up to the sky.

"Where is he!? Where did it take him?" Ginger squealed, her hands covering her mouth.

"Do you really think he knows?" Buford said back, scratching his forehead in shock at what had just happened. "That thing came out of nowhere!"

"You got that right." Adyson remarked.

Ferb took Isabella's hand and stepped in front of her view in order to make her look at him. Her cheeks were stained with tears and she breathed unsteadily, causing Ferb even more pain to see. Isabella was his best friend, -or even better-a sister, and he would do anything in order for her to be safe and sound. It made his heart ache to see her like this, and he was sure his facial expression at the moment wasn't helping her at all. They just stared at each other, Isabella knowing exactly what was going on in his genius brain. Years of being by him in their adventures had trained her mind's eye to see into his overly complicated skull, and she could tell what he wanted to get across to her.

They were going to find that bloody triangle and get their triangle back.

Isabella fell into his warm embrace, and hugged him tightly, short cries coming from her body and her chest heaving. Ferb held her close and tried really ireally/i hard not to start crying himself, because this was his brother- His very own brother that had been taken right out of the grasp of Isabella. The same brother he had vowed to himself to always keep safe no matter what the issue. And he couldn't have done anything to stop that rancid beast from stealing Phineas away from him. It happened so fast-A little too fast for either of them to be able to hold back their tears.

"Well, are we just gonna stand here and cry all night, or are we going to find where Phineas was taken?" Milly said, putting the one question down on the table that was lingering at the back of everyone's brains. "I for one do not want to have a crying Izzy at all, and a crying Ferb is definitely not the next thing we need." She crossed her arms.

Gretchen tapped her fingers together in thought. "What should we do, Ferb?" She stepped forward and looked up at the boy and Isabella who stood on the table. "Who was that… thing?"

Everyone went silent, as they all had no idea what it was, and all eyes fell upon the green-haired Brit. He knew that everyone wanted an explanation from him, so he slowly pulled away from Isabella and wiped her face of tears. "It's going to be okay, everyone." He murmured softly. Ferb looked out at the now empty yard. Everyone had left besides the usual gang.

They all looked up to Ferb, and he knew it. He couldn't simply tell them that he had no idea what to do or what that blithering thing was, because that would scare them out of their minds and nobody would be able to sleep tonight. Not even Buford. Because whatever that triangular thing was, it had scared the living daylights out of Ferb, and it wasn't normal for him to be scared of anything.

"I'm not going to just let this slide without a fight. I don't know where he is, but with all of the justice in me, I_ will_ find my stepbrother, and I will bring him home, and I don't give a crap about how long it takes."

Gretchen smiled then, and so did a few others, but Isabella still had misty eyes.

Isabella wiped her eyes, trying to get rid of all the running mascara that made them turn bloodshot. She sniffed twice in a row, and fixed her hair before she turned to face the others. "Guys, we need some time to think about this so… Everyone should go ahead and head home. We'll talk about this tomorrow."

"But Chief!" Gretchen called, but Isabella stopped her by jumping off the table.

"Please, everyone, just leave." She said more firmly this time, and all of the Fireside girls gave her hugs and left. Buford and Baljeet were more reluctant to go, but with a warm hug to both of them from Isabella, they turned and left.

Gretchen stayed though, even though Isabella turned towards her and gave her an annoyed look.

"I'm not going to leave, Isabella. Phineas just disappeared on my _birthday_. I am not going to just call it a night and go home when I know this was probably my fault!"

"How was this your fault Gretchen?" Isabella's voice quaked.

The girl pushed up her glasses and her eyes began to cloud over. "I don't know! Maybe all the commotion made that thing come?" She threw her arms up into the air. "I am not going to just let that slide. Please let me help you guys!"

Ferb jumped down and joined them on the grass.

Isabella looked at Ferb as if asking his approval that she could help. She had nothing against Gretchen helping, she just didn't know if Ferb would mind.

"If you truly wish to help, just understand that this may be dangerous." The usual spark in his eyes had gone somewhere, leaving a very non expressive look to Ferb's face. Almost the same as it had been all those years ago when he had first moved here…

Gretchen nodded without a single second wasted. "Yes! Yes, I don't care. You know I've joined you in things you've done in the past. I wanna help as much as I can."

Ferb gave her a small smile only to reassure her. "Alright. But… you two may want to change into some more comfortable clothing. I know I'll be up all night trying to figure anything out, so if you want you can go put on some night clothes." The girls cut him off by nodding in return.

"Yeah, these outfits are meant for fancy situations, not grave ones." Isabella said, and they both ran out of the yard in five seconds flat.

Ferb stood in his place until the gate stopped squeaking back and forth. He looked out at the yard and then gasped, reaching a hand up to his forehead. He then let out a frustrated sigh.

"I guess no one here knew what a rubbish bin was…"

While he began to pick up after everybody because he simply did not feel like making a quick robot to do it for him, the girls ran over to Isabella's house to get some comfy clothes. Isabella was going to let Gretchen borrow some because her house wasn't even in the neighborhood.

They both ran past Vivian, who was a little bit too endorsed in a television show to notice the sound of footsteps behind the couch. Gretchen followed Isabella up the stairs and into her room.

Once they were safely inside, Isabella pulled out her pajama drawer. "Okay, I have lots of sweatpants and stuff to wear. What color do you like best? I have… pink… pink… and um… pink..." She frowned.

"Why do you only have pink?" Gretchen giggled.

Isabella pulled out a pair that had a bejeweled princess crown on the left upper leg. "I don't know…"

Gretchen smiled and took a pair from her. "That's okay, pink is fine." She paused for a moment to examine them before she began to change. "So… are we going to keep this a secret from our parents or what?"

Isabella took a deep breath. "I'm gonna tell my mom that there's gonna be a sleepover at Phineas and Ferb's house and just the gang is gonna be there. She trusts everyone enough to let me stay late."

"But what about my mom and dad?"

Isabella handed her a tank top to put on. It was also pink. "Tell them you're sleeping over with me."

"But I've never lied to them before!"

"It's okay Gretch, if you end up having to tell them the truth, it's not like we're doing anything wrong. Ferb's not that kind of guy." Isabella brushed her hair after getting her own tank top on.

Gretchen pressed her lips together in acceptance. "Yeah… I guess you're right. Plus, my party isn't even supposed to be over anyway." She smiled.

Isabella handed her the brush, and she took it.

"That dress was so tight." Gretchen muttered as she gave the sparkly piece of expensive fabric that laid on Izzy's bed a disgusted look. "I'm glad to be out of that thing."

"You looked so good in it!" Isabella complimented. She raised her eyebrows and chuckled. "You were catching a lot of attention…"

Gretchen's eyes went wide. "Was it that bad!?"

"That's not a bad thing!" Isabella said loudly.

"Yes it is! I don't want attention from boys yet, I still have to get through college! I have an education on the line here!" She sighed. "Oh, I knew it was a mistake to get it."

Isabella shook her head slowly. "Gretchen, look at you. What are you saying? You're gonna make yourself get through college before you start dating!? I thought we've already been through this!"

"We have, Chief, and you have a completely different mindset than me." She laughed.

Isabella smiled at her and rolled her eyes. "Well… then what made you get the dress even though you knew it would get attention?"

Gretchen blinked at her. "I don't know."

Isabella eyed her suspiciously. "You're lying."

"I'm not lying!" She said as her face started to turn pink.

Isabella paused and looked at her through the mirror. "There has to be a reason!"

"Well, there's not, I just liked the dress! It looked marvelous on that mannequin and I just… I liked it okay!?" She started to nervously fold the thing.

"Gretchen, now I know for a fact that you're lying. You start to fold things when you lie."

"No I don't!"

Isabella crossed her arms and glanced from the dress to her and back again twice.

"It just needed to be folded, I'm a bit OCD!" She glanced at the bed and made a quick adjustment to the covers, passing a hand over them to force the wrinkles out.

"No you're not." A clever grin crept up her lips and made a dimple on her cheek visible.

"How would you know?" She sat on the bed.

"Because I've known you since we were in kindergarten." Isabella laughed. "And if you were, you wouldn't have just messed the bed back up by sitting on it."

Gretchen swallowed nervously and twirled a piece of loose string in the quilt around her finger. "Let's just go back to the backyard, okay?"

Isabella was then reminded of the reason why they were even in her room in the first place. She bit her lip as her eyes trailed straight to the picture beside her bed containing none other than Phineas Flynn. Gretchen had done a good job at helping her forget him.

She forced herself to look back at Gretchen who was a nervous wreck for some reason that she didn't know, and Isabella sighed slowly. "Okay. Ferb's probably wondering what's taking so long, anyway." She paused as Gretchen stood back up. "But don't think that this conversation is over, Commander."

Gretchen slumped down as she made her way out of the bedroom. "Yes Sir…"

Isabella shut the door behind her and they both made their way back to the backyard.

Ferb had finished any cleaning that needed to be done, leaving all the lights and decorations because frankly he didn't feel like dealing with them right now. He had brought his laptop outside and was fiddling with it under the tree when the girls arrived in the backyard.

All of the lights had been turned off, and the dance floor was now gone, leaving only the grass to sit on. Ferb had changed too, and was now sporting some purple flannel pajama pants and a T-shirt.

"Hey Phi-Ferb… um…What'cha dooin?" Isabella asked sadly.

The sound of the voice made him look up, and seeing that they were both now wearing some comfy attire, he smiled and gave them a small wave of the hand.

"No really, Ferb what are you doing?" She pressed.

The boy blinked. He wasn't used to having to answer that question, so he just… hadn't. "Oh, I'm trying to see if this thing has been seen by anyone else."

"That's a good start." Gretchen said as the two girls sat down on either side of him to look at the screen. On it, there were two different tabs open and they were split down the center of the screen so that he could see both at the same time.

"The internet is the only logical place to look first. I mean, I don't recall having any books about yellow talking triangular kidnappers."

"Do you think it was some kind of…" Isabella trailed off as she began to read some of the suggestions Google had given them, and most had websites about geometrical shapes.

"I don't know what to think." Ferb said. "Everything I've tried hasn't pulled up a single thing relevant to what I'm looking for."

"Why do you have two separate internets open?" Isabella questioned, pointing at them.

"In case I find something on one and I want to look something else up on the other."

"Why don't you just open a new tab?" Gretchen said, leaning in to see it better.

"Because I like to be able to see everything I'm looking at at one time. And since Phineas won't give me the password for the holographic computer, I can't work on that one."

The girls both simultaneously let out the same noise. "Ohhh…"

Ferb smiled a bit at that, and then erased what he had typed in in the search bar for Google.

"Have you tried looking up entities? It was glowing so maybe it was some kind of creepy thing like that." Gretchen suggested.

"The only thing I've tried so far is 'living Eye of Providence' and 'creepy talking triangles'." He sighed softly. "But it wouldn't hurt to try that."

He typed in 'evil triangular entities' and tapped enter.

The first thing to show up in the list was a website for a Mystery Shack apparently.

"Evil dream demon." Ferb read. "Click to read more." He raised his eyebrows.

"Click on it, it sounds about right." Isabella said, pulling her legs up to her chest and wrapping her arms around them.

So Ferb did exactly that. The website was fully decorated with a background that looked like old brown wood and an orange bar on the top of the screen that listed off different pages on the site. The first button read "Buy Merchandise", the second read "Absolutely Real Creatures", the third labeled "Activities", the fourth with "Directions to Here", and the fifth reading "ROGUE DEMON ON THE LOOSE. CLICK THIS."

The front home page only gave a picture of this "Mystery Shack" but the S was missing and the sign only said "Mystery hack", and below it said, _"Want a super awesome and mind bending tour containing some of the most elusive creatures known to mankind? You've come to the right place! Stop by the Mystery Shack, the house of mystery, and have your mind blown today! Don't forget your wallets."_

"This just looks like some dumb tourist trap." Isabella muttered.

Gretchen shook her head and looked closely at the screen, eying the words carefully. "I don't know, Izzy, this might be something important. Take a look at the label on that button in the navigation bar."

Ferb moved the mouse up to the button that read "ROGUE DEMON ON THE LOOSE. CLICK THIS" and clicked it.

It took a minute before the page pulled up. The wifi in the tree wasn't all that strong. They had installed it about five years ago, so it didn't surprise anyone that it was getting a bit wobbly. But once the page did pull up, they all gasped simultaneously. There was a very accurate drawing of the thing they had seen. The thing that had taken Phineas.

"THAT'S IT! THAT'S THE THING!" Isabella shouted, as if neither of her friends knew.

There was a short paragraph below the picture, and Gretchen pushed up her glasses and read:

_ "If you're reading this right now, please DO NOT stop. I don't think my Great Uncle would approve of me hacking the Shack's website but… I need to get this out there in case somebody needs help. If you have seen the thing in the picture above, do not interact with it. It is an evil demon by the name of Bill, and is EXTREMELY dangerous._ The girl stopped and continued to read in silence, not being able to utter a sound because of how frightening the message was.

"Whoever this guy is, we need to go meet him." Isabella ordered.

Ferb nodded. He took a screen capture of the drawing of the demon and saved it to his pictures, and then added the website to his bookmarked pages. He then went back one page, returning to the home screen, and clicked the button "Directions to Here".

It pulled up a map of a place called Gravity Falls.

"Oregon? This guy lives in Oregon?" Gretchen said after seeing the labels on the map.

"Then what in the world was this Bill guy doing here? And why did he take Phineas!?" Isabella exclaimed with wide eyes as she turned her gaze from the computer screen to Ferb.

"That's what I was thinking." Gretchen concurred. "What would he want with Phin? He's just a normal… well… abnormal teenager."

Ferb stared at the screen a minute longer while the girls talked.

"And it seemed so happy about stealing him away from us!" Isabella yelled. "I wouldn't be surprised if it was just all for fun and games… I mean, he was wearing a bow tie, for goodness sake!"

"Well, there have been some really serious and meaningful men that bore bow ties on their suits."

"But that wasn't a guy, Gretch! _THAT_ was a _TRIANGLE_!"

"Phineas is a triangle too." She added.

"Yeah, but at least _he_ has a heart!"

Ferb leaned his head back until it fell against the bark of the tree.

"Isabella, you need to calm down." Gretchen said soothingly.

"HOW DO YOU EXPECT ME TO CALM DOWN WHEN A DEMONIC TRIANGLE RIPPED PHINEAS OUT OF MY OWN ARMS?"

Gretchen let out a sorrowful sigh and looked down just as Ferb shut the lid of his laptop.

"I could have held onto him tighter… or… or pushed him out of the way or… or something!" The raven-haired Jewish Mexican girl said though shaky breaths. "If I can't stop this from happening, then how am I gonna stop even worse things from happening in the future?" She passed two jittery hands through her hair on the top of her head. "Oh, what am I talking about, what could be worse than this?"

"Isabella, just take a deep breath in, and let it out slowly." Gretchen said. "Hyperventilation is not helpful during dire situations."

Isabella did just that, filling her chest with air and then waiting a few pulses before letting it out through her nose. She then looked up at Ferb with her big blue pleading eyes.

"Ferb?"

The boy lifted his head off the trunk to look her in the eye.

"What are we gonna do? If the person we need to get to is in Oregon, and we're like five states away from him, how are we going to know how to get Phineas back? I mean, I don't think this is one of those situations that can be handled over the phone, Ferb. We need to meet up with this Mystery Shack person and confront with him."

Ferb tapped his fingers on the lid of the laptop and raised his eyebrows before looking at Gretchen and back to Isabella. "Well," He began. "That means we need to catch the very next flight to Gravity Falls, which is, apparently, just west of Weird, one of the major cities in Oregon. So… In other words, Isabella, I know what we're going to do today."

"Tonight." Gretchen corrected sadly.

Ferb frowned slightly. "…Tonight."

* * *

**DUN DUN DUNNNNNNNNN**

**Please pardon my extreme amount of seriousness in this chapter. I feel like it's way too much. :p Also I tend to make Ferb a bit OOC, but it makes sense because it's hard to write for a character that doesn't talk much. Sometimes you kind of have to make him talk, especially when he also has a serious lack of facial expressions. Pleas review! Thanks for reading! Next chapter will be posted soon.  
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**Also if you are really desperate (which I doubt any of you are) to know how this will go, you can just go to my DeviantArt page (same username, HalyPooH) and chapters 1-11 are posted there in my gallery. If you are not familiar to dA, to get to my gallery there is a little button with the Mona Lisa on it at the top of the page. **


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